The story tells the story of a pair of twin brothers Tianling (older brother) and Tianling (younger brother) who are often mistaken for women. After their parents mysteriously disappeared, due to financial difficulties and the suggestion of their younger brother, the elder brother Tianling was forced to work in a maid cafe as a woman. In the process, they met a series of "women" (including pretenders and transformed people) with different personalities and extraordinary abilities, and gradually revealed that they were not ordinary humans, but "princesses" with mermaid blood. A mysterious transformation made them completely become biological women and awakened their mermaid form. Afterwards, they entered a special academy and started a campus life full of comedy, daily life and fantasy with these acquainted and new characters (many of whom are lesbians or sister control/sister control), involving multiple identity disguises, emotional entanglements, and the display of supernatural powers. The core of the story lies in the gender and species transformation of the two protagonists, and how they adapt to and explore these new identities.